1. Field of the Invention
Aspects of the present invention relate to a toner dispensing system, and a method for controlling the same.
2. Description of the Related Art
In a general electrophotographic printing process of an image forming apparatus, for example, a printer, a photocopier, a facsimile machine, or a multi-functional product, a photoreceptor (i.e. a photosensitive drum) is electrically charged, and is then exposed to a light pattern corresponding to an original image, whereby the surface of the photoreceptor is selectively discharged to form a latent image. After the latent image is recorded on the photoreceptor, developer material is applied to the photoreceptor to develop the latent image. Toner particles are attracted to the latent image to form a toner image on the photoreceptor. The toner image is then transferred from the photoreceptor to a printable medium, such as a sheet of paper. The toner particles are then fused into the sheet of paper, through a fusing unit, to fix a permanent image to the sheet of paper.
Process control software in image forming apparatuses, such as digital electrophotographic printers and copiers can count the actual number of pixels per page. Pixel counting has been used to estimate the amount of toner used in developing an image. The estimated value, representing the amount of toner consumed, is used to control a process of adding toner to a developer housing in a dual component development system, and to indicate the remaining amount of toner in a toner cartridge in a single component development system. In the dual component development system, for example, the toner concentration is maintained uniformly, while the image forming apparatus is in operation, to maintain print quality. To accomplish this, toner may be added to the developer housing, in a controllable fashion, during the entire printing process. In the single component development system, toner consumption is monitored, and a warning signal is given to the user when an “End of Life” condition is nearly reached.
However, when only the pixel count is used, it is not possible to describe different types of images, such as text/line, halftone, and solid area images, for which different amounts of toner are consumed. Due to the fringe field development effect, different types of images consume different amounts of toner for the same pixel count. Thus, the estimation method using only the pixel count is inaccurate.
U.S. Pat. No. 6,810,218 discloses an estimation method for different types of images using a pixel count and a pixel transition count. In this method, the ratio between the transition count (laser on/off or off/on) and the pixel count, are used to determine which type of image is most greatly exposed on the photoreceptor. Then, different amounts of toner used per pixel, depending on image types, are incorporated into the algorithm to provide a better estimation of toner usage.
The main feature of the U.S. Pat. No. 6,810,218 is to provide a method of more accurately estimating toner usage in the single component system using the pixel count and the transition count in the algorithm. This algorithm is used to generate a more accurate gas gauge that reflects a value close to an actual remaining toner ratio (%). When the printer has a hard stop (i.e., when the printer is stopped as the gas gauge indicates 0%), the actual remaining toner ratio approaches zero, if the gas gauge is accurate. However, U.S. Pat. No. 6,374,064 does not disclose an algorithm that uses transition and pixel counts, in the dispensing system, to replenish the toner consumed in the dual component development system.
U.S. Pat. No. 6,374,064 discloses a dispensing system that is controlled according to a combination of pixel dispensing, toner concentration (TC) dispensing, and patch dispensing, in an algorithm, to replenish toner consumed when developing a latent image. The dispensing system replenishes consumed toner, in a controllable fashion, in a dual component development system. However, the dispensing system uses only the pixel count no matter what type of image is dominant in the image. This dispensing system also uses only one dispensing rate regardless of the print job length, i.e., whether the print job length is long or short, or whether or not the print job is continuous. Without considering the job length, the dispensing system may fail to accurately determine the amount of toner to be dispensed to replenish consumed toner.